Optical apparatus

ABSTRACT

A first surface of an optical component has a lens function of converging the transmission light from a light source. A second surface reflects the transmission light, converged by the lens function of the first surface, towards an end face of an optical transmission medium as the destination of transmission. The light reflected by the second surface is radaited from a coupling surface. Since the light beam from the light source is directed towards the optical transmission medium by exploiting the total reflection of light, a high-reflection multi-layer film or a polarization beam splitter film, required in a conventional apparatus employing a polarization beam splitter, is unneeded, with the result that the film forming cost or the cost in bonding two prisms used for fabricating the polarization beam splitter may be dispensed with. In this manner, the production cost or size of the apparatus can be reduced without lowering the transmission/reception performance.

RELATED APPLICATION DATA

The present application is a 37 C.F.R. §1.53(b) continuation of U.S.patent application Ser. No. 09/486,360, filed Feb. 25, 2000. ThroughU.S. patent application Ser. No. 09/486,360, U.S. Pat. No. 6,433,942 thepresent application claims priority to PCT Patent Application No.PCT/JP99/03452, filed Jun. 28, 1999, which claims priority to JapanesePatent Application No. P10-1 81153, filed Jun. 26, 1998, each of whichapplication is incorporated herein by reference to the extent permittedby law.

TECHNICAL FIELD

This invention relates to an optical apparatus suitable fortransmission/reception of e.g., signal light for optical communication.

BACKGROUND ART

In these years, in keeping up with information diversification, thus iswith the tendency towards multi-media, development of a small-sized,high-performance low-cost communication apparatus has become adesideratum. The optical communication by a two-core optical fiber,having a glass optical fiber for transmission and a glass optical fiberfor reception, has already been put to practical use because it permitshigh transmission rate and long-distance transmission and also becauseit is strong against electromagnetic noise. However, in the opticalcommunication employing the two-core optical fiber, the optical fiberand the communication apparatus are both expensive, such that it is notused extensively in households and finding only limited practicalapplication. Thus, the recent tendency is towards communicationemploying a sole inexpensive plastic optical fiber, such thatpreparations are being made for a communication environment by auni-core optical fiber.

FIGS. 37 and 38 mainly show the schematic structure of opticalcomponents of a conventional optical communication apparatus employing auni-core optical fiber. FIGS. 37 and 38 show an optical path L11 of thetransmitting light along with the schematic structure of an opticalsystem of the optical communication apparatus and an optical path L12 ofthe transmitting light along with the schematic structure of the opticalsystem of the optical communication apparatus.

As shown in these figures, the optical system of the communicationapparatus includes a light source 101 constructed by e.g., asemiconductor laser for radiating a transmitting laser light beam, and acollimator lens 102 for converting the light from the light source 101into collimated light and for radiating a collimated light beam. Theoptical system also includes a polarization beam splitter 103 forreflecting the S-polarized component of the incident light substantiallyby total reflection and transmitting a P-polarized component of theincident light substantially by total transmission. The optical systemalso includes a coupling lens 104 for converging the transmitting lightradiated from the polarization beam splitter 103 on an end face 105 a ofa uni-core optical fiber 105 and for radiating the received lightradiated from the end face 105 a of the optical fiber 105 as acollimated light beam. The optical system also includes a converginglens 106 for converging the collimated light beam radiated from thecoupling lens 104, and a photodetector 107 for detecting the receivedlight converged by the converging lens 106. The polarization beamsplitter 103 includes an inclined surface 103 a on the surface of whicha dielectric multilayer film is formed for imparting a polarization beamsplitter function, that is for reflecting an S-polarized light componentof the incident light substantially by total reflection and fortransmitting a P-polarized light component thereof substantially bytotal transmission. In the transmitting/reception device, the lightsource 101 and the polarization beam splitter 103 are arranged so thatthe plane of polarization of light radiated from the light source 101 tofall on the inclined surface 103 a will the S-polarization plane. Thus,the light from the light source 101 (S-polarized light) undergoessubstantially total reflection on the inclined surface 103 a.

In the above-described circuit apparatus, employing the polarizationbeam splitter 103, bidirectional optical communication, that istransmission and reception employing the laser light, becomes possiblewith the use of a sole device.

The optical communication in the transmission apparatus capable ofbidirectional optical communication occurs as follows:

Referring first to FIG. 37, when light is transmitted from the circuitapparatus, the transmitting light is radiated from a light source 101and collimated by the collimator lens 102 to fall on the polarizationbeam splitter 103. Since the light source 101 and the polarization beamsplitter 103 are arranged relative to each other so that the plane ofpolarization of the light radiated from the light source 101 to fall onthe inclined surface 103 a will be the P-polarized light, the lightradiated from the light source 101 is reflected substantially by totalreflection by the inclined surface 103 a. The light beam reflected bytotal reflection by the inclined surface 103 a falls on the end face 105a of the optical fiber 105 via the coupling lens 104. The light incidenton the optical fiber 105 is transmitted through the optical fiber 105 tothe destination of communication as the signal light for communication.

Referring to FIG. 38, the signal light transmitted through the opticalfiber 105 at the time of light reception by the communication apparatusis radiated from the end face 105 aof the optical fiber 105. The lightbeam of the signal light radiated from the end face 105 ais collimatedby the coupling lens 104 of the communication apparatus so as to fall onthe polarization beam splitter 103. The light beam incident on thepolarization beam splitter 103 has a random plane of polarization (lightof random polarization). Of the light beam incident on the polarizationbeam splitter 103, the S-polarized light component is reflectedsubstantially by total reflection by the inclined surface 103 a so as tobe radiated towards the light source 101 as the so-called feedbacklight. On the other hand, of the light beam incident on the polarizationbeam splitter 103, the P-polarized light is transmitted through theinclined surface 103 a substantially by total transmission to exit thepolarization beam splitter 103. The light radiated from the polarizationbeam splitter 103 is converged by the converging lens 106 on thephotodetector 107, which then detects the light converged by theconverging lens 106 on photoelectric conversion as a reception signal.

Thus, with the communication apparatus shown in FIGS. 37 and 38,employing the polarization beam splitter 103, bidirectional opticalcommunication employing the laser light becomes possible even though noother device is used.

The polarization beam splitting function of the above-describedpolarization beam splitter is realized by forming a film structuredescribed below on an optical component.

As the technique of adding an optical function, such as theabove-mentioned polarization beam splitter function, to an opticalelement, the operation of optical interference, as occurs when settingthe film thickness of a transparent thin film to a value of the numberof orders of light wavelength, is frequently used.

It is noted that the condition of interference when the light falls onthe sole layer film in a perpendicular direction is shown by thefollowing equation:

n×d=m(¼)×λ

where λ is the light wavelength, n the refractive index of a monolayerfilm, m an number of orders of interference and d is a physical filmthickness. In general, in the above equation, n×d is termed the opticalfilm thickness, while the number of orders of interference m is termedthe phase thickness of a quarter wave optical thickness (QWOT). Forexample, in the case of a thin film in which the wavelength λ of thelight used is 550 nm, the refractive index of the monolayer of 2.3 andthe physical film thickness d of 59.78 nm, the optical film thickness(n×d) is 137.5 nm, with the optical film thickness, that is the numberof orders of interference m, being 1.

Meanwhile, if a single coating or a monolayer is formed on a substrateas an optical element, there are two boundary surfaces having differentrefractive indexes between the air and the film, that is a boundarysurface between the air and the film (first boundary surface), and aboundary surface between the film and a substrate of the optical element(secondary surface). If, in such case, the phase thickness, that is thenumber of orders of interference m, is an odd number, phase deviation πoccurs, so that, as may be seen from the above equation, the reflectedwaves from the first boundary surface (boundary surface between air andthe film) and the reflected waves from the second boundary surface (theboundary surface between the film and the substrate) interfere with eachother to give the operation of the reflected waves cancelling each otherto a maximum extent. On the other hand, if the phase thickness, that isthe value of the number of orders of interference m, is an even number,the phase matching occurs, so that, as may be seen from the aboveequation, the reflected waves from the first boundary surface (boundarysurface between the air and the film) and those from the second boundarysurface (boundary surface between the film and the substrate) reinforceeach other. Meanwhile, if the value of the phase thickness, that is thenumber of orders of interference m, is not an integer, there is producedan action lying intermediate between the case where the number of ordersof interference is an odd number and that where the number of orders ofinterference is an even number. Thus, it may be seen that the action oflight interference can be controlled by changing the value of therefractive index of the film and the value of the physical filmthickness d.

In the above-described polarization beam splitter 103, there is used athin film structure by multiple layers obtained on alternately layeringa thin film of high refractive index and a thin film of low refractiveindex. The interference operation in the case of the multi-layer film ishereinafter explained.

The optical properties by the action of light interference can becomputed by a matrix method employing the optical impedance. Forexample, if the film refractive index is n, film thickness is d and anangle of incidence of light to the film is θ, the characteristic matrixof a transparent monolayer film can be expressed by the followingtwo-row two-column four-terminal matrix: $M = \begin{bmatrix}{m11} & {m12} \\{m21} & {m22}\end{bmatrix}$

where m11, m22 are represented by cosg (m11=m22=cos g), m12 isrepresented by i·sing/u (m12=i·u·sing) and m21 is represented byi·u·sing (m21=i·u·sing). On the other hand, g is represented by2·π(n·d·cos θ)/λ (g=2·π(n·d·cos θ)/θ). For S-polarized light and forP-polarized light, u=n·cos λ and u=n·sec θ, respectively.

The characteristic matrix M of a multi-layer film is represented by theproduct of characteristic matrices M1, M2, . . . , Mi, where i is aninteger not less than 1, as indicated by the following equation:

M=(M 1)×(M 2)×. . . ×(Mi).

At this time, the reflectance R of the multi-layer film may becalculated, from the respective elements of the above-mentioned productof the characteristic matrices, the refractive index n0 of an incidentmedium and a refractive index ns of the substrate, by the followingequation:$R = {\frac{{( {{m11} + {i \cdot {m12} \cdot {us}}} ) \cdot {u0}} - ( {{i \cdot {m21}} + {{m22} \cdot {us}}} )}{{( {{m11} + {i \cdot {m12} \cdot {us}}} ) \cdot {u0}} + ( {{i \cdot {m21}} + {{m22} \cdot {us}}} )}}^{2}$

where u0=n0·cos θ0, us=ns·cos θs for the S-polarized light component andu0=n0·sec θ0, us=ns·sec θs for the S-polarized light component.

The above-described polarization beam splitter 103 may be realized by analternate layering structure of two sorts of thin-film materials havingrefractive indices satisfying the so-called Brewster condition.

A more specified illustrative designing of a polarization beam splitteris hereinafter explained.

It is assumed that a polarization beam splitter obtained on bonding twoprisms having apex angles of 45° is to be designed as a substrate of apolarization beam splitter. Also, in the present embodiment, thedesinging wavelength is 780 nm, and a vitreous material for a prism isSF11 (number of optical glass manufactured by SCHOTT INC.). A highrefractive index thin film material used is TiO₂, with a refractiveindex of 2.30, whilst a low refractive index material used is SiO₂ witha refractive index of 1.46.

Since TiO₂ with the refractive index of 2.30 and SiO₂ with therefractive index of 1.46 are used as the high refractive index materialand the low refractive index material, respectively, as a filmcombination satisfying the Brewster condition, polarizationcharacteristics satisfying the functions of the polarization beamsplitter can be obtained by alternately layering TiO₂ and SiO₂ as shownbelow. It is noted that a multi-layer film composed of first tosixteenth layers is formed.

first layer TiO₂, d=93.9 nm, nd=216.0 mn

second layer SiO₂, d=147.9 mn, nd=215.9 mn

third layer TiO₂, d=93.9 nm, nd=216.0 nm

fourth layer SiO₂, d=147.9 nm, nd=215.9 nm

fifth layer TiO₂, d=93.9 nm, nd=216.0 mn

sixth layer SiO₂, d=147.9 nm, nd=215.9 nm

seventh layer TiO₂, d=93.9 nm, nd=216.0 nm

eighth layer SiO₂, d=147.9 nm, nd=215.9 nm

ninth layer TiO₂, d=93.9 nm, nd=216.0 nm

tenth layer SiO₂, d=147.9 nm, nd=215.9 nm

eleventh layer TiO₂, d=93.9 nm, nd=216.0 nm

twelfth layer SiO₂, d=147.9 nm, nd=215.9 nm

thirteenth layer TiO₂, d=93.9 nm, nd=216.0 nm

fourteenth layer SiO₂, d=147.9 nm, nd=215.9 nm

fifteenth layer TiO₂, d=93.9 nm, nd=216.0 nm

sixteenth layer SiO₂, d=147.9 nm, nd=215.9 nm

That is, of the first to sixteenth layers, odd-numbered layers, that isthe first, third, fifth, seventh, ninth, eleventh, thirteenth andfifteenth layers, are of TiO₂, whilst even-numbered layers, that issecond, fourth, sixth, eighth, tenth, twelfth, fourteenth and sixteenthlayers are of SiO₂. Moreover, the physical thickness d of the TiO₂ layeras an odd-numbered layer is set to, for example, 93.9 nm, whilst thephysical thickness d of the SiO₂ layer as an even-numbered layer is setto, for example, 147.9 nm. In addition, an optical film thickness nd ofa TiO₂ layer as an odd-numbered layer is set to 216.0 nm, with opticalfilm thickness nd of a SiO₂ layer as an even-numbered layer is set to215.9 nm.

Meanwhile, the optical communication apparatus employing theabove-described polarization beam splitter suffers from the followingproblems:

First, the polarization beam splitter is in need of high operationalreliability, so that the multi-layered film needs to be fabricated by anexpensive electron beam evaporator, whilst there are a large number offilm layers and a prism needs to be bonded after formation of themulti-layered film, thus increasing the manufacturing cost considerably.

On the other hand, the polarization beam splitter has such opticalcharacteristics that it has high light incident angle dependency, suchthat, in order to secure the signal to noise ratio of the communicationlight (communication signals), it is mandatory to provide a collimatorlens for collimating the light beam. Moreover, it is necessary to effectoptical axis alignment.

In addition, the conventional optical communication apparatus has adrawback that it has a large number of optical components to renderintegration difficult.

That is, the conventional optical communication apparatus has a drawbackthat its manufacturing cost is prohibitive and the apparatus tends to beincreased in size.

In view of the above-depicted problem of the prior art, it is an objectof the present invention to provide an optical apparatus whereby, if theapparatus is used as an optical communication apparatus, it reduces thecost and size of the apparatus without lowering the communicationperformance.

DISCLOSURE OF THE INVENTION

The present invention provides an optical apparatus including a mainbody unit of an optical apparatus, an optical transmission mediumconnector for connecting the optical transmission medium to the mainbody unit of the optical apparatus so that an end face of the opticaltransmission medium is at a pre-set angle with respect to the main bodyunit of the optical apparatus, a light emitting element fixed in themain body unit of the optical apparatus and adapted for radiating thelight, and a sole optical element having a second surface facing thefirst surface and a connecting surface interconnecting the first andsecond surfaces. The sole optical element is fixed to the main body unitof the optical apparatus. The first surface has the function ofconverging a light beam of light incident thereon from outside so thatthe light beam is focussed at a position spaced a pre-set distance fromthe first surface. The light emitting element, optical component and theoptical transmission medium connector are secured in the main body unitof the optical apparatus in a relative position such that light radiatedfrom the light emitting element is incident on the optical component viathe first surface, the light incident on the first surface traverses theinside of the optical component, the light which has traversed theinside of the optical component is reflected on the second surface ofthe optical component towards the optical transmission medium connector,the light reflected on the second surface is radiated from the couplingsurface to outside the optical component, and the light outgoing fromthe coupling surface is focussed on an end face of the opticaltransmission medium.

In the optical apparatus according to the present invention, there isalso provided a light receiving element at a position lying on theoptical axis of the light radiated from the light transmission medium ofthe main body unit of the optical apparatus.

The optical component is arranged offset from the optical axis of thelight radiated from the optical transmission medium.

The optical component is arranged on the optical axis of the lightradiated from the optical transmission medium. The light radiated fromthe optical transmission medium falls on the coupling surface in theoptical component via the coupling surface to traverse the inside of theoptical component to fall on the light receiving element.

The optical transmission medium connector connects the opticaltransmission medium at an angle with which the optical axis of the lightradiated from the optical transmission medium is inclined with respectto the optical axis direction of the light radiated from the lightemitting element to get to the second surface.

The optical transmission medium connector connects the opticaltransmission medium at an angle such that the optical axis of the lightradiated from the optical transmission medium is included in a planeperpendicular to the optical axis direction of light radiated from thelight emitting element to get to the second surface of the opticalcomponent.

The light receiving element is arranged on the opposite side of thelight emitting element with respect to the second surface of the opticalcomponent.

The light receiving element is arranged on the side of the lightemitting element with respect to the second surface and the lightradiated from the optical transmission medium falls on the opticalcomponent via the coupling surface to traverse the inside of the opticalcomponent to fall on the light receiving element.

The optical component has a diffractive pattern on the first surface.

The optical component further has a third surface which is provided atan area between the second surface and the coupling surface which is atleast proximate to the optical transmission medium connector.

The first surface of the optical component is such that thecross-section obtained on slicing the optical component in a planepassing through a first optical axis of light radiated from the lightemitting element and getting to the second surface and through a secondoptical axis of light radiated from the optical transmission medium isconvexed towards the light emitting element.

The first surface of the optical component is such that thecross-section obtained on slicing the optical component in a first planeperpendicular to a second plane passing through a first optical axis oflight radiated from the light emitting element and getting to the secondsurface and through a second optical axis of light radiated from theoptical transmission medium is convexed towards the light emittingelement, with the first plane passing through the first optical axis.

The optical component has a substantially circular cross-sectional shapewhich is obtained on slicing the optical component in a planeperpendicular to an optical axis of light radiated from the lightemitting element and getting to the second surface.

The second surface exhibits total reflection characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematics of an optical communication apparatus accordingto a first embodiment of the present invention.

FIG. 2 illustrates total reflection conditions of a reflection surfaceof an optical component in the optical communication apparatus shown inFIG. 1.

FIG. 3 illustrates a specified illustrative designing of an opticalcomponent in the optical communication apparatus shown in FIG. 1.

FIG. 4 is a perspective view of a casing of the optical communicationapparatus according to the present invention.

FIG. 5 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 1, arranged in a casing.

FIG. 6 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a second embodiment of the presentinvention.

FIG. 7 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 1, arranged in a casing.

FIG. 8 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a third embodiment of the presentinvention.

FIG. 9 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 8, arranged in a casing.

FIG. 10 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a fourth embodiment of the presentinvention.

FIG. 11 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 10, arranged in a casing.

FIG. 12 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a fifth embodiment of the presentinvention.

FIG. 13 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 12, arranged in a casing.

FIG. 14 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a sixth embodiment of the presentinvention.

FIG. 15 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 14, arranged in a casing, and looking from theside of an arrow A in FIG. 15.

FIG. 16 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 14, arranged in a casing, and looking from theside of an arrow A in FIG. 15.

FIG. 17 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a seventh embodiment of the presentinvention.

FIG. 18 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 17, arranged in a casing.

FIG. 19 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to an eighth embodiment of the presentinvention.

FIG. 20 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 19, arranged in a casing.

FIG. 21 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a ninth embodiment of the presentinvention.

FIG. 22 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 21, arranged in a casing.

FIG. 23 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a tenth embodiment of the presentinvention.

FIG. 24 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 23, arranged in a casing.

FIG. 25 is a perspective view showing a first specified embodiment ofoptical communication apparatus of the various embodiments of thepresent invention.

FIG. 26 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 25.

FIG. 27 is a see-through perspective view showing the state in which theoptical communication apparatus employing the optical component of FIG.25 is arranged in a casing.

FIG. 28 is a perspective view showing a second specified embodiment ofoptical communication apparatus of the various embodiments of thepresent invention.

FIG. 29 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 28.

FIG. 30 is a see-through perspective view showing the state in which theoptical communication apparatus employing the optical component of FIG.25 is arranged in a casing.

FIG. 31 is a perspective view showing a third specified embodiment ofoptical communication apparatus of the various embodiments of thepresent invention.

FIG. 32 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 31.

FIG. 33 is a see-through perspective view showing the state in which theoptical communication apparatus employing the optical component of FIG.31 is arranged in a casing.

FIG. 34 is a perspective view showing a fourth specified embodiment ofoptical communication apparatus of the various embodiments of thepresent invention.

FIG. 35 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 34.

FIG. 36 is a see-through perspective view showing the state in which theoptical communication apparatus employing the optical component of FIG.34 is arranged in a casing.

FIG. 37 is a diagrammatic view showing schematics of a conventionaloptical communication apparatus.

FIG. 38 is a diagrammatic view showing schematics of anotherconventional optical communication apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, certain preferred embodiments of the presentinvention will be explained in detail.

FIG. 1 shows a schematic arrangement of an optical system, as a mainportion of an optical communication apparatus 10 for opticalcommunication enabling transmission and reception of changes in lightintensity as an optical apparatus embodying the present invention. InFIG. 1, there are also shown an optical path L1 of the transmissionsystem and an optical path L2 of the reception system, along with thearrangement of the optical apparatus.

The optical communication apparatus 10 of the first embodiment includesa light source 1, constituted by a semiconductor laser or a lightemitting diodes to emit the transmission light for opticalcommunication, an optical component 2 for guiding the transmission lightfrom the light source 1 to an end face 4 a of an optical transmissionmedium 4 formed by, for example, a unit-core optical fiber, and aphotodetector 3 for detecting the receiving light emitted from the endface 4 a of the optical transmission medium 4 as reception signal.

In the present optical communication apparatus 10, shown in FIG. 1, thelight source 1, optical component 2 and the photodetector 3 are arrangedin a congested configuration in different areas on a substrate 11 of,for example, a semiconductor integrated circuit. The light source 1 isarranged in a congested fashion on the substrate 11 via a support base12. The photodetector 3 has its portion other than its detection surfaceburied in the bulk portion of the substrate 11 of, for example, asemiconductor integrated circuit, with a detection surface being on anoptical axis of the light radiated from the end face 4 a of the opticaltransmission medium 4 and being at a position facing the end face 4 a ofthe optical transmission medium 4.

Also, in the optical communication apparatus 10 of FIG. 1, thephotodetector 3 is arranged on an optical axis of the light radiatedfrom the end face 4 a of the optical transmission medium 4, whilst theoptical component 2 is arranged at a position offset from the opticalaxis of the reception light radiated from the end face 4 a of theoptical transmission medium 4. Stated differently, the respectiveconstituent elements of the optical communication apparatus 10 arearranged so that the reception light radiated from the end face 4 a ofthe optical transmission medium 4 is incident only on the photodetector3 without being incident on the optical component 2. Also, in theoptical communication apparatus 10 of the embodiment of FIG. 1, theoptical path L1 of the transmission system is arranged so as not to beoverlapped with the optical path L2 of the reception system.

The optical component 2 of the optical communication apparatus 10 isformed of a sole transparent optical material and has a lens functionand a prism function. Meanwhile, the lens function in the opticalcomponent 2 means light beam converging, numerical aperture (NA)converting functions etc, and realizes the lens function of convergingthe light beam or converting the NA by the spherical surface,non-spherical surface or the shape of the diffraction lattice. Also, theprism function in the optical component 2 means the function of changingthe spatial direction of the light beam, such as reflection,transmission reflection or diffraction. Also, in the present embodiment,the reflection in the prism function of the optical component 2 meanstotal reflection of light occurring on the boundary surface between anoptically dense medium (medium of high refractive index) and anoptically sparse medium (medium of low refractive index) when the lightproceeding in the optically dense medium falls on the optically sparsemedium.

The optical component 2 includes a first surface S1 (lens surface S1)facing the light source 1 and adapted to converge the transmitted lightfrom the light source 1 at a position offset a pre-set distance, and asecond surface S2 (reflecting surface S2) provided facing the lenssurface S1 and adapted to reflect the transmission light converged bythe lens function of the lens surface S1 towards the end face 4 a of theoptical transmission medium 4. The optical component 2 also includes abonding surface S3 to the substrate 11 and a surface S4 operating as aradiating surface for radiating the light reflected by the reflectingsurface S2. The surface S4 is referred to below as a coupling surface S4because it operates for coupling the first surface S1 to the secondsurface S2. Meanwhile, in the optical component 2, it is desirable forthe lens surface S1 and the coupling surface S4 to form ananti-reflective surface for reducing the stray light or optical loss.Also, the lens surface S1 and the coupling surface S4 may be subjectedin the optical component 2 to refractive index profile processing. Inparticular, the lens surface S1 is preferably provided with amulti-layer reflection preventative film to achieve anti-reflectioneffect over a wide angle of incidence.

Also, in the optical component 2, the lens surface S1 producing the lensfunction has its focal length or the NA designed so that the light beamemitted by the light source 1 will form a focal point on the end face 4a of the optical transmission medium 4. In the optical component 2, thereflecting surface S2 is a surface responsible for the above-mentionedprism function and is adapted for reflecting the incident light by thetotal reflection of light generated on the interface between theoptically dense medium and the optically sparse medium. That is, thisreflecting surface S2 is inclined at a pre-set angle with respect to theoptical axis of the light radiated from the light source 1 so as toproduce total reflection of the incident light.

Referring to FIG. 2, the relation between the angle of incidence to thereflective surface S2 of the optical component 2 and the condition oftotal reflection of light by the reflecting surface S2.

For aiding in the understanding of the optical operation by the opticalcomponent 2, it is assumed that the light beam of the transmitted lightfrom the light source 1 is the light beam only along the direction ofthe directive line, that is that the light beam of the transmitted lightis a collimated light beam. Meanwhile, the direction of the directiveline means the center vector direction of the light beam from the lightsource 1.

The angle of incidence θi of the transmitted light on the reflectingsurface S2 is expressed by the equation (A):

θi=θ ₂₃−90°  (A)

where θ₂₃ is an angle between the reflecting surface S2 and the surfaceS3. It is noted that the angle of incidence θi is an angle between aline of orientation P1 and a normal line P2 drawn to the reflectingsurface S2. In FIGS. 1 and 2, the angle the reflecting surface S2 makeswith the surface of the substrate 11 is denoted with a reference symbolθ₂₄.

On the other hand, critical angle θc of total reflection of light isexpressed by the following equation (B):

θc=sin⁻¹(1/ng)  (B)

where ng is the refractive index of the optical component 2.

It is noted that, if the angle of incidence θi is larger than or equalto θc, that is if θi≧θc, total reflection occurs on the reflectingsurface S2. Therefore, the condition for the angle θ₂₃ is represented,from the equations A and B, by the following equation (C):

θ₂₃≧90°+sin⁻¹(1/ng)  (C).

FIG. 3 shows a computational example for angles θc and θ₂₃ in case ofapplying a material routinely used as an optical material. In FIG. 3,there is shown a computational example for the angles θc and θ₂₃ in caseof application of a quartz glass and an optical glass BK7 and SF11,manufactured by SCHOTTS INC, as a material routinely used as an opticalmaterial. FIG. 3 shows computational examples for the angles θc and θ₂₃in case of applying the polymethyl methacrylate (PMMA) and polycarbonate(PC) as typical plastics materials for optical application. As may beseen from FIG. 3, it is sufficiently possible, in a majority of routineoptical materials, to realistically design the optical components 2 inwhich the reflecting surface S2 brings about total reflection. As mayalso be seen from FIG. 3, if a material of high refractive index is usedas the optical component 2, the critical angle θc is reduced to renderit possible to reduce the angle θ₂₃.

In the above explanation, the light beam incident on the reflectingsurface S2 is assumed to be a collimated light beam. However, inactuality, the light beam incident on the reflecting surface S2 is thelight beam converged by the lens operation of the lens surface S1, sothat the angle of incidence on the reflecting surface S2 has an angularextent determined by the angle of convergence of the light beam andhence there is a risk that a light beam be produced which is not inmeeting with the condition for total reflection. If, on the other hand,the laser light is used as the transmitting light, the intensity of thelaser light exhibits the Gaussian distribution, such that the centerintensity is high whilst the intensity on the skirts is extremely low.Therefore, if in actuality the angle θ₂₃ is increased with theconverging angle Δθ (half angle) as an offset, ideal total reflection isachieved even with the converging light beam. If, on the other hand, thedevice size is to be decreased at the cost of the S/N ratio of thedevice to a slight extent, the angle θi (=θ₂₃−90°) may be equal to thecritical angle θc of total reflection without taking the angle ofconvergence into account. The light of an angular range for which theincidence angle of the light beam to the reflecting surface S2 is notlarger than the critical angle θc is in the skirt range of the laserlight exhibiting the Gaussian distribution, that is the range where thelight intensity is extremely low, so that a sufficiently usable S/Nratio can be obtained.

In the optical transmission apparatus, constructed as shown in FIG. 1,the light transmitting and receiving operation is the following:

First, or light transmission from the optical transmission apparatus,the transmitting light is radiated from the light source 1. The lightbeam of the transmitted light, radiated by the light source 1, isconverged by the lens surface S1 of the optical component 2, arrangedfacing the light source 1, and proceeds through the interior of theoptical component 2. The light beam incident from the lens surface S1 istotally reflected by the reflecting surface S2 and radiated via couplingsurface S4 towards an end face 4 a of the optical transmission medium 4.The light beam radiated from the optical component 2 forms an image onthe end face 4 a of the optical transmission medium 4 by the lensoperation of the lens surface S1. The light beam incident on the endface 4 a proceeds as transmission signal through the opticaltransmission medium 4 and gets to an optical transmission apparatus ofthe destination of transmission.

For light reception in the present optical transmission apparatus, thesignal light transmitted through the optical transmission medium 4 isradiated from the end face 4 a of the optical transmission medium 4. Thesignal light radiated from the end face 4 a is radiated on thephotodetector 3. This photodetector 3 photo-electrically converting theincident light, while detecting changes in the intensity of the incidentlight. The signal light incident on the end face 4 a of the opticaltransmission medium 4 and transmitted through the optical transmissionmedium 4 is detected as a received signal. Preferably, ananti-reflection film or a filter film transmitting only the signal light(received light) is provided on the surface of the photodetector 3 totransmit only the wavelength of the received light to reduce the opticalloss to remove stray light. By providing the filter film or the like, itis possible for the photodetector 3 to detect substantially the totalityof the received light to improve the S/N ratio of the apparatus at thetime of reception.

The above-described optical communication apparatus, embodying thepresent invention, is arranged in a casing 20 shown for example in FIG.4. To the casing 20 can be connected the optical transmission medium 4as an optical fiber vis a connector 21.

FIG. 5 shows a cross-sectional view of the components parts of FIG. 1arranged in the casing 20 of FIG. 4. In FIG. 5, a substrate 11, on whichare assembled the support base 12, optical component 2 and thephotodetector 3, is secured to the inner bottom surface of the casing20. On the connector 21 is mounted an optical fiber as the opticaltransmission medium 4. The relation between the fixed position of thesubstrate 11 and the arranging position of the connector 21 on thecasing is such that the photodetector 3 on the substrate 11 is on theoptical axis of the light radiated from the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21.

In the optical communication apparatus 10 of the first embodiment,described above, in which the respective optical elements are arrangedso that the optical path L1 of the transmission system will not beoverlapped with the optical path R2 of the receiving system, thepolarization beam splitter for separating the transmitting light fromthe receiving light, so far used in the conventional opticalcommunication apparatus, becomes unnecessary. Also, in the opticalcommunication apparatus 10 of the first embodiment, since the light beamfrom the light source 1 is guided towards the optical transmissionmedium 4 by exploiting the phenomenon of total reflection of lightgenerated on the boundary surface (reflecting surface S2) on lightincidence from an optically dense transparent medium to a roughtransparent optical medium, it is unnecessary to form a high reflectionmulti-layered film or a polarization beam splitter film, incontradistinction from the conventional apparatus employing thepolarization beam splitter, thus enabling reduction in costs, such asthe cost in forming films or in bonding two prisms used formanufacturing polarization beam splitters.

Also, in the present first embodiment, in which the action of totalreflection of light on the reflecting surface S2 of the opticalcomponent 2 is exploited, the light is reflected on the reflectingsurface S2 at 100% reflectance, without regard to the angle of lightincidence, insofar as the condition for total light reflection is met.The reflection on the reflecting surface S2 exhibits extremely smallincident angle dependency, so that, if substantially the totality of theconverged light from the lens surface S1 is reflected by the reflectingsurface S2, the transmitted light suffers from only small loss, as aresult of which the deterioration of the S/N ratio is evaded. Thus, inthe present first embodiment, the collimator lens for maintaining theS/N ratio as required in the conventional device is not needed to renderit possible to diminish the number of components. Moreover, since theoptical communication apparatus of the present first embodiment uses theoptical component 2 having both the lens and prism functions and whichintegrates the functions of plural optical components, the number of theoptical components can be diminished, at the same time as integrationwith semiconductor components such as the light source 1 or thephotodetector 3 of the semiconductor laser is facilitated to render itpossible to reduce the size of the apparatus and the assembling cost.Also, since the optical component 2, as a sole component, has thefunction as a lens and that as a prism, in combination, it isunnecessary to have plural components, such as polarization beamsplitter, as in the conventional device, so that the optical component 2can be manufactured by a method having high mass-producibility, such asglass pressing or injection molding of plastics, thus enabling costreduction.

In addition, in the present embodiment of the optical communicationapparatus, since the optical path L1 of the transmitting system is notoverlapped with the optical path Reflecting surface S2 of the receptionsystem, and hence there is no return light of the received light to thelight source 1, no laser noise is produced. Moreover, the conventionalapparatus employing the polarization beam splitter discards theS-polarized component of the received light, thus deteriorating the S/Nratio at the time of reception. Conversely, the present embodiment ofthe optical communication apparatus, employing an optical systemexhibiting no polarization dependency of light, has a superior S/N ratioat the time of reception.

Thus, in the present embodiment, the apparatus can be reduced in sizeand cost without lowering the transmission and reception performance.

Referring to FIGS. 6 and 7, a second embodiment of the present inventionis explained. In the following description, parts or components whichare the same as those of the first embodiment are depicted by the samereference symbols and are not explained specifically.

FIG. 6 shows schematics of an optical communication apparatus 10Aaccording to a second embodiment of the present invention. In theabove-described first embodiment, the optical component 2 and thephotodetector 3 are arranged on respective different areas in thesubstrate 11. In the present second embodiment of the opticalcommunication apparatus 10A, the optical component 2 is arranged on thesame area on the substrate 11 as that in which the photodetector 3 isburied in the substrate 11. Stated differently, the optical component 2is arranged on the optical axis of the received light, radiated from theend face 4 a of the optical transmission medium 4 is incident via thecoupling surface S4 of the optical transmission medium 4 to traverse theinterior of the optical component 2 to fall on the photodetector 3.Also, in the present second embodiment, the optical component 2 and thephotodetector 3 are arranged so that the optical component 2 has itssurface S3 bonded to a detection surface of the photodetector 3.

Thus, in the present second embodiment, the signal light, transmitted bythe optical transmission medium 4, is radiated from the end face 4 a ofthe optical transmission medium 4 to fall on the optical component 2 viathe coupling surface S4. The light incident from the coupling surface S4on the optical component 2 is radiated from the surface S3 to reach thephotodetector 3 so as to be detected as a reception signal.

In the present embodiment, the device can be smaller in size than thedevice of the first embodiment by arranging the optical component 2 andthe photodetector 3 in the same region of the substrate 11.

Meanwhile, in the present second embodiment, the optical component 2 issecured to the photodetector 3. As an adhesive, a transparent adhesiveis used to prevent the detection performance of the photodetector 3 frombeing lowered. Also, in the present embodiment, since the received lightfalls on the coupling surface S4 of the optical component 2 to get tothe photodetector 3 via the surface S3, the latter is preferablyprocessed for preventing light reflection. If the surface S3 is to beprocessed for reflection prevention, it is preferred to performreflection prevention processing taking into account the refractiveindex and the thickness of the transparent adhesive.

Also, in the present second embodiment, it is preferred to use amaterial of a refractive index higher than that of the material used inthe first embodiment. If the material of a higher refractive index isused, the critical angle θc of total reflection on the reflectivesurface S2 is decreased such that the condition for total reflection onthe reflecting surface S2 of the totality of the light beams incident onthe reflecting surface S2 is more liable to be met. Also, in the case ofthe optical component 2, formed of a high refractive index material, therefractive power on the lens surface S1 can be increased, as thecondition for total reflection on the lens surface S1 is met, so that itis possible to reduce the focal length from the lens surface S1 to theend face 4 a of the optical transmission medium 4 and hence to reducethe size of the apparatus.

Referring to FIG. 7, the optical communication apparatus 10A of theabove-described second embodiment is arranged in the casing 20A similarto that shown in FIG. 4. Meanwhile, FIG. 7 shows a cross-section of thecomponents of FIG. 6 arranged in the casing 20A. In the followingdescription, parts or components which are the same as those of thefirst embodiment are depicted by the same reference symbols and are notexplained specifically.

In the second embodiment, the relative position between the mountingposition of the substrate 11 and a connector 21A is such that theoptical component 2 and the photodetector 3 on the substrate 11 will bearranged on the optical axis of the light radiated from the end face 4 aof the optical transmission medium 4 mounted on the connector 21A.

In the above-described second embodiment of the optical communicationapparatus 10A, in which the optical component 2 and the photodetector 3are arranged on the same area of the substrate 11, the apparatus can befurther reduced in size.

Also, with the present second embodiment of the optical communicationapparatus 10A, as in the first embodiment, the polarization beamsplitter, so far used for separating the transmission light and thereception light from each other, becomes unnecessary, so that it becomesunnecessary to form a high reflection multi-layered film or apolarization beam splitter film, thus allowing to reduce the costsincurred in film deposition or bonding two prisms used for manufacturingthe polarization beam splitter. Moreover, in the present secondembodiment, as in the first embodiment, the transmission light can bereflected substantially in its entirety on the reflecting surface S2, sothat loss in the transmission light is reduced, while a collimator lensfor assuring the S/N ratio performance as required in the conventionalapparatus is redundant to render it possible to reduce the number ofcomponents. Also, in the optical communication apparatus 10A of thesecond embodiment, as in the first embodiment, the optical component 2,which has integrated plural optical components, is used, thus allowingto reduce the number of optical components, the size of the apparatusand the assembling costs and to facilitate integration of respectivecomponents. Moreover, the optical component 2 can be produced by amanufacturing method of high mass-producibility to allow for costreduction. Also, in the optical communication apparatus 10A of thesecond embodiment, similarly to the first embodiment, there is no returnlight of the reception light to the light source 1, no laser noise etcis produced. Moreover, the S/N ratio on reception is excellent becausethe optical system having no light polarization dependency is used.

Referring to FIGS. 8 and 9, a third embodiment of the present inventionis explained. In the following description, parts or components whichare the same as those of the first embodiment are depicted by the samereference symbols and are not explained specifically.

FIG. 8 shows schematics of the optical communication apparatus 10Baccording to an embodiment of the present invention. In the opticalcommunication apparatus 10B of the present third embodiment, thephotodetector 3 is arranged on the optical axis of the reception lightradiated from the end face 4 a of the optical transmission medium 4,whilst the optical component 2 is arranged at a position offset from theoptical axis of the reception light radiated from the end face 4 a ofthe optical transmission medium 4.

Also, in the present third embodiment, an angle θ₂₃, which thereflecting surface S2 of the optical component 2 makes with the surfaceS3 is set to 135°, that is the angle the reflecting surface S2 makeswith the surface of the substrate 11 is set to 45°. At this time, thematerial of the optical component 2 needs to be such a material assatisfies the conditions for total reflection even with the angle θ₂₃ of135°. Meanwhile, the optical materials shown in FIG. 3 all satisfy theconditions for total reflection even if the angle θ₂₃is set to 135°. Itis noted that the ant-reflection processing needs to be performed on thelens surface S1 and the coupling surface S4.

Since the angle θ₂₃ is set in the present third embodiment to 135°, thelight converging position of the transmission light is substantiallydirectly above the reflecting surface S2. Therefore, the end face 4 a ofthe optical transmission medium 4 is arranged substantially directlyabove the reflecting surface S2. However, the optical transmissionmedium 4 is tilted so that the optical axis of the reception lightradiated from the optical transmission medium 4 will be outside theoptical component 2 with respect to the light source 1. Since theoptical transmission medium 4 has its end tilted, in the present thirdembodiment, the signal light transmitted by the optical transmissionmedium 4 is radiated from the end face 4 a of the optical transmissionmedium 4 so as to be radiated on the photodetector 3 without falling onthe optical component 2.

The optical communication apparatus 10B of the above-described thirdembodiment is arranged in the casing 20B, as shown in FIG. 9. FIG. 9shows a cross-section of the respective components of FIG. 8 enclosed inthe casing 20B.

In the present third embodiment, the connector 21B connects the opticaltransmission medium 4 at an angle such that the optical axis of theradiated light from the end face 4 a of the optical transmission medium4 is inclined with respect to the plane perpendicular to the directionof the optical axis of the transmission light radiated from the lightsource 1 to get to the reflecting surface S2 of the optical component 2.That is, in the present third embodiment, the connector 21B is arrangedso that the optical transmission medium 4 will be arranged obliquelyrelative to the casing 20B. Also, the connector 21B is arranged with atilt relative to the optical component 2 and the photodetector 3 so thatthe end face 4 a of the optical transmission medium 4 mounted on theconnector 21B faces the reflecting surface S2 of the optical component2, the optical axis of the reception light radiated from the opticaltransmission medium 4 is outside the optical component 2 with respect tothe light source 1, and so that the radiated light from the opticaltransmission medium 4 will fall only on the photodetector 3 withoutfalling on the optical component 2.

With the above-described third embodiment of the optical communicationapparatus 10B, in which the angle θ₂₃ in the reflecting surface S2 ofthe optical component 2 is set to 135°, the optical component 2 can bemanufactured easily at a low cost.

Referring to FIGS. 10 and 11, a fourth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

FIG. 10 is a diagrammatic view showing the schematics of an opticalcommunication apparatus 10C according to the fourth embodiment of thepresent invention. The optical communication apparatus 10C of the thirdembodiment has both the feature of the above-described second and thirdsembodiments. That is, in the present fourth embodiment of the opticalcommunication apparatus 10C, the optical component 2 is arranged on theoptical axis of the reception light radiated from the end face 4 a ofthe optical transmission medium 4, the reception light radiated from theend face 4 a of the optical transmission medium 4 will be incident onthe coupling surface S4 of the optical component 2 to fall on thephotodetector 3 via the interior of the optical component 2 and theangle θ₂₃ on the reflecting surface S2 of the optical component 2 is setto 135° C.

In the present fourth embodiment, the optical transmission medium 4 isarranged so as to directly overlie the reflecting surface S2 of theoptical component 2, while being tilted at a distal end thereof so thatthe light beam of the reception light radiated from the end face 4 awill be incident from the coupling surface S4 to get to thephotodetector 3 via the surface S3 without falling on the reflectivesurface S2. Meanwhile, in the present fourth embodiment, the directionof tilt of the optical transmission medium 4 is opposite to that in thethird embodiment.

In the present fourth embodiment, the signal light transmitted by theoptical transmission medium 4 tilted in the opposite direction to thatin the third embodiment is radiated from the end face 4 a of the opticaltransmission medium 4 to fall on the optical component 2 via thecoupling surface S4. The light incident on the optical component 2reaches the photodetector 3 via the surface S3 so as to be detected bythis photodetector 3 as a reception signal.

The optical communication apparatus 10C of the above-described fourthembodiment is arranged in the casing 20C, as shown in FIG. 11. FIG. 11shows a cross-section of the respective component parts of FIG. 10arranged in the casing 20C.

In the present fourth embodiment, the connector 21C connects the opticaltransmission medium 4 at an angle with which the optical axis of thelight radiated at the end face 4 a of the optical transmission medium 4is inclined relative to the casing 20C. That is, in the present fourthembodiment, the connector 21C is provided so that the opticaltransmission medium 4 will be inclined obliquely relative to the casing20C. The connector 21C is located relative to the optical component 2and the photodetector 3 so that the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21C is inclined in anopposite direction to that in the embodiment of FIG. 9 and so that theoptical component 2 and the photodetector 3 will be arranged on theoptical axis of the light radiated from the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21C.

With the above-described fourth embodiment of the optical communicationapparatus 10C, since the optical component 2 and the photodetector 3 arearranged on the same area of the substrate 11, and the angle θ₂₃ on thereflecting surface S2 of the optical component 2 is set to 135°, it ispossible to reduce the size and the cost of the apparatus further.

Also, with the above-described fourth embodiment of the opticalcommunication apparatus 10C, as in the first to third embodiments, it ispossible to reduce the size and the production cost of the apparatus,while it is possible to reduce the deterioration in the signal S/Nratio.

Referring to FIGS. 12 and 13, a fifth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

FIG. 12 is a diagrammatic view showing the schematics of an opticalcommunication apparatus 10F according to the fifth embodiment of thepresent invention. In the present fifth embodiment, the photodetector 3is arranged between the light source 1 and the optical component 2. Inthe present fifth embodiment, the optical transmission medium 4 isarranged at a pre-set tilt so that the reception light radiated from theend face 4 a will be illuminated on the photodetector 3. Specifically,with the present fifth embodiment, the photodetector 3 is arranged onthe optical axis of the reception light radiated from the end face 4 aof the optical transmission medium 4, whilst the optical component 2 isarranged at a position offset from the optical axis of the receptionlight radiated from the end face 4 a of the optical transmission medium4.

The arrangement of the present fifth embodiment is suitably used if, dueto the constraint form apparatus designing, the photodetector 3 cannotbe arranged opposite side of the reflecting surface S2 of the opticalcomponent 2 looking from the light source 1 as in the above-describedfirst and third embodiments, or if it is desired to prevent the loweringof the light volume of the reception light caused by providing thephotodetector 3 below the optical component 2.

The optical communication apparatus 10F is arranged within the casing20F, as shown in FIG. 13, showing the respective component parts of FIG.12 arranged in the casing 20F in a cross-sectional view.

In the present fifth embodiment, the connector 21F connects the opticaltransmission medium 4 at an angle with which the optical axis of thelight radiated from the end face 4 a of the optical transmission medium4 is inclined relative to the plane perpendicular to the direction ofthe optical axis of the transmission light radiated from the lightsource 1 to get to the reflecting surface S2 of the optical component 2.That is, in the present fifth embodiment, a connector 21F is providedfor connecting the optical transmission medium 4 obliquely relative tothe casing 20F. Also, the connector 21F is arranged so that the opticalaxis of the light radiated from the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21F is on thephotodetector 3 arranged between the light source 1 and the opticalcomponent 2.

In the fifth embodiment of optical communication apparatus 10F, in whichthe photodetector 3 can be arranged between the photodetector 3 and theoptical component 2, it is possible to raise the degree of freedom inapparatus designing to prevent the lowering of the light volume of thereception light.

With the fifth embodiment of the optical communication apparatus 10F, aswith the first to fourth embodiment, it is possible to reduce the sizeand the production cost of the apparatus, while it is possible toprevent the signal S/N ratio from being lowered.

Referring to FIGS. 14 to 16, a sixth embodiment of the present inventionis explained. In the following description, parts or components whichare the same as those of the first embodiment are depicted by the samereference symbols and are not explained specifically.

FIG. 14 is a diagrammatic view showing the schematics of an opticalcommunication apparatus 10G according to the sixth embodiment of thepresent invention. In the present sixth embodiment, the photodetector 3is arranged on the optical axis of the reception light radiated from theend face 4 a of the optical transmission medium 4, whilst the opticalcomponent 2 is arranged at a position offset from the optical axis ofthe reception light radiated from the end face 4 a of the opticaltransmission medium 4. In addition, the arranging angle of the opticaltransmission medium 4 is tilted so that the optical axis of thereception light radiated from the optical transmission medium 4 will beinclined relative to the plane which contains the optical axis radiatedfrom the light source 1 to get to the reflecting surface S2 and which isperpendicular to the substrate 1. Meanwhile, the reflecting surface S2of the optical component 2 is inclined so that the angle between it andthe substrate 11 will be equal to the aforementioned angle θ₂₃.

The optical communication apparatus 10G of the above-described fourthembodiment is arranged in a casing 20G, as shown in FIG. 15, showing across-section of the respective component parts of FIG. 14 arranged inthe casing 20G. Meanwhile, FIG. 16 shows a cross-section showing thestate in which the optical communication apparatus 10G of the sixthembodiment is arranged in the casing 20G, with the optical communicationapparatus 10G being viewed from the direction of an arrow A in FIG. 15.

That is, in the present sixth embodiment, the connector 21G is arrangedon the casing 20, so that the optical axis of the reception lightradiated from the end face 4 a of the optical transmission medium 4 willbe inclined relative to the plane containing the optical axis of thelight radiated from the light source 1 to get the reflecting surface S2and which is perpendicular to the substrate 11, as shown in FIGS. 15 and16.

The optical communication apparatus 10G of the present sixth embodimentis suitably employed if, due to constraint in apparatus designing, theconnector 21G cannot be arranged at right angles to the casing surface,as when the optical transmission medium 4 cannot be arranged at rightangles to the casing surface, or if the photodetector 3 cannot bearranged on a plane containing the optical axis of the light radiatedfrom the light source 1 to get to the reflecting surface S2 and which isnormal to the substrate 1.

With the present sixth embodiment, the configuration of theabove-described third to fifth embodiments can be used in combination.That is, in the above-described third to fifth embodiments, as in thesixth embodiment, the arranging angle of the optical transmission medium4 can be tilted so that the optical axis of the reception light radiatedfrom the optical transmission medium 4 will be inclined with respect tothe plane containing the optical axis of the light radiated from thelight source 1 to get to the reflecting surface S2 and which is normalto the substrate 1.

In the present sixth embodiment, the optical axis of the transmissionlight radiated by the light source so as to be reflected by thereflecting surface S2 traverses a plane containing the optical axis ofthe light radiated from the light source 1 to get to the reflectingsurface S2 and which is normal to the substrate 1. Alternatively, theoptical axis of the transmission light radiated from the light source 1and which is reflected by the reflecting surface S2 may be inclinedrelative to the plane containing the optical axis of the light radiatedfrom the light source 1 to get to the reflecting surface S2 and which isnormal to the substrate 11. However, in this case, the reflectingsurface S2 needs to be inclined at the aforementioned angle of θ₂₃ tothe substrate 11 and also needs to be inclined relative to the planeperpendicular to the optical axis the light radiated from the lightsource 1 to get to the reflecting surface S2.

In the above-described sixth embodiment of the optical communicationapparatus 10G, in which the optical transmission medium 4 can bearranged so that the optical axis of the reception light radiated fromthe end face 4 a of the optical transmission medium 4 will be inclinedrelative to the plane containing the optical axis of the light radiatedfrom the light source 1 to get to the reflecting surface S2 and which isnormal to the substrate 11, it is possible to raise the degree offreedom in apparatus designing.

With the sixth embodiment of the optical communication apparatus 10G, aswith the first to sixth embodiments, it is possible to reduce the sizeand the production cost of the apparatus, while it is possible toprevent the signal S/N ratio from being lowered.

Referring to FIGS. 17 and 18, a seventh embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

FIG. 17 is a diagrammatic view showing the schematics of an opticalcommunication apparatus 10E according to the seventh embodiment of thepresent invention.

In the above-described first embodiment, the reflecting surface S2 ofthe optical component 2 intersects the coupling surface S4 at an acuteangle. In the present seventh embodiment of the optical communicationapparatus 10E, the region of the optical component 2 where thereflecting surface S2 intersects the coupling surface S4, that is the atleast a portion of the reflecting surface and the coupling surface S4close to the optical transmission medium 4, is provided with a cut-outsurface S5. Meanwhile, FIG. 17 shows an example in which the cut-outsurface S5 is provided in the optical component 2 in case the respectivecomponents of the optical communication apparatus 10E are arrangedsimilarly to the arrangement of FIG. 1. However, the cut-out surface S5may similarly be provided on the optical component 2 of the thirdembodiment shown in FIG. 8 or on the optical component 2 of the sixthembodiment shown in FIG. 14.

The optical communication apparatus 10E of the above-described seventhembodiment is arranged in a casing 20, as shown in FIG. 18, showing across-section of the respective component parts of FIG. 17 arranged inthe casing 20.

In the above-described seventh embodiment of the optical communicationapparatus 10E, in which the cut-out surface S5 is provided at an area ofintersection of the reflecting surface S2 of the optical component 2 andthe coupling surface S4, it is possible to prevent the reception lightradiated by the end face 4 a of the optical transmission medium 4 toproceed towards the photodetector 5 from being kicked by the opticalcomponent 2, as well as to prevent the optical component 2 from beingangled acutely. This gives a merit that the optical component 2 can beimproved in safety in operation to render the optical component 2 morerobust against destruction.

In the optical communication apparatus 10E of the seventh embodiment, asin the first to sixth embodiments, it becomes to reduce the cost andsize of the apparatus as well as to prevent deterioration of the S/Nratio.

Using FIGS. 19 and 20, an eighth embodiment of the present invention isexplained. In the following description, parts or components which arethe same as those of the first embodiment are depicted by the samereference symbols and are not explained specifically.

FIG. 19 shows a diagrammatic view showing the schematics of an eighthembodiment of the optical communication apparatus 10D. In the eighthembodiment of the optical communication apparatus 10D, shown in FIG. 9,a diffraction grating pattern is formed on the lens surface S1 of theoptical component 2.

In the present eighth embodiment, in which the diffraction gratingpattern is formed on the lens surface S1 of the optical component 2, thelens function ascribable to diffraction is added to the lens surface S1,with the result that the refraction power can be increased, while thecorrection for aberration is facilitated. Meanwhile, the diffractiongrating pattern such as used in the eighth embodiment may be provided onthe lens surface S1 of the optical component 2 of each of the first toseventh embodiments.

The optical communication apparatus 10D of the above-described eighthembodiment is arranged in a casing 20, as shown in FIG. 20, showing across-section of the respective component parts of FIG. 19 arranged inthe casing 20.

In the above-described eighth embodiment of the optical communicationapparatus 10D, in which the diffraction grating pattern is formed on thesurface S1 of the optical component 2, the diffractive power can beincreased to reduce the size of the apparatus.

Also, in the present eight embodiment of the optical communicationapparatus 10D, as in the first to seventh embodiments, it is possible toreduce the size and the production cost of the apparatus, while it ispossible to prevent the signal S/N ratio from being lowered.

Referring to FIGS. 21 and 22, a ninth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

FIG. 21 is a diagrammatic view showing the schematics of an opticalcommunication apparatus 10H according to the ninth embodiment of thepresent invention. In the present ninth embodiment of the opticalcommunication apparatus 10H, shown in FIG. 21, the light convergingaction and the refractive action of changing the optical axis directionare afforded to the lens surface S1 of the optical component 2. That is,the lens surface S1 of the optical component 2 in the present ninthembodiment converges the light radiated from the light source 1 in thesimilar manner to the aforementioned respective embodiments, whilebending the optical axis of the light radiated from the light source 1so that the optical axis will be offset at an angle indicated by θ_(off)shown in FIG. 21. Also, in the present eighth embodiment, the angle θ₂₅which the optical axis after refraction by the lens surface S1 makeswith the reflective surface S2 will meet the aforementioned condition ofthe critical angle θc. Stated differently, in the present ninthembodiment, the angle θ25 which the optical axis after refraction by thelens surface S1 makes with the reflective surface S2 is designed to meetthe condition of the critical angle θc even though the optical axis ofthe light radiated from the light source 1 is bent so that the opticalaxis is offset an angle θ_(off) by the lens surface S1. In this case,the light radiated from the light source 1 to be incident on thereflecting surface S2 undergoes total reflection on the reflectionsurface S2. Moreover, in the eighth embodiment, the light reflected bythe reflecting surface S2 falls on the end face 4 a at substantially theright angle. The light reflected by the end face 4 a of the opticaltransmission medium 4 falls in this manner on the end face 4 a of theoptical transmission medium 4 at substantially the right angle, wherebylow dispersion is achieved.

On the other hand, in the ninth embodiment, the reception light radiatedfrom the end face 4 a of the optical transmission medium 4 falls on thecoupling surface S4 of the optical component 2 and on the reflectingsurface S2 in this order. It is noted that the angle which the opticalaxis of the reception light radiated from the end face 4 a of theoptical transmission medium 4 makes with the reflecting surface S2 is anangle θ26 not satisfying the aforementioned critical angle θc. In otherwords, in the present ninth embodiment, the reflecting surface S2 has atilt satisfying the critical angle θc capable of reflecting thetransmission light incident via the lens surface S1 by total reflection,however, the tilt is such that the reception light radiated from the endface 4 a of the optical transmission medium 4 is transmitted since itfails to meet the condition of the critical angle θc. That is, thereception light transmitted through the reflection surface S2 isreceived by the photodetector 3 arranged on the optical axis of thereception light radiated from the end face 4 a of the opticaltransmission medium 4.

The above-described ninth embodiment of the optical communicationapparatus 10H is arranged in the casing 20, as shown in FIG. 22, showinga cross-section of the respective component parts of FIG. 21 arranged inthe casing 20.

In the present ninth embodiment of the optical communication apparatus10H, the transmission light falls on the end face 4 a of the opticaltransmission medium 4 at substantially the right angle, whereby lowdispersion is achieved. Moreover, since the photodetector 3 can bearranged below the reflecting surface S2, the apparatus can be reducedin size.

Also, in the present ninth embodiment of the optical communicationapparatus 10H, as in the first to eighth embodiments, it is possible toreduce the size and the production cost of the apparatus, while it ispossible to prevent the signal S/N ratio from being lowered.

Referring to FIGS. 21 and 22, a tenth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

FIG. 23 is a diagrammatic view showing the schematics of an opticalcommunication apparatus 10I according to the tenth embodiment of thepresent invention. In the above-described ninth embodiment, thediffractive action of offsetting the optical axis of the light radiatedby the light source 1 is afforded to the lens surface S1 of the opticalcomponent 2. In the present tenth embodiment, the support base 12carrying the light source 1 is tilted to tilt the optical axis of thelight radiated from the light source 1 by an angle θ_(off) relative tothe substrate 11. By so doing, the lens surface S1 of the opticalcomponent 2 of the tenth embodiment having only the lens function as inthe aforementioned first embodiment can be used, whilst the angle θ₂₅which the optical axis of the outgoing light from the light source 1makes with the reflection surface S2 can be set to an angle satisfyingthe condition of the critical angle θc.

In the tenth embodiment, the reception light radiated from the end face4 a of the optical transmission medium 4 falls on the coupling surfaceS4 of the optical component 2 and on the reflecting surface S2 in thisorder. At this time, the angle which the reception light radiated fromthe end face 4 a of the optical transmission medium 4 makes with thereflecting surface S2 is an angle θ₂₆ not satisfying the condition ofthe critical angle θc. Thus, the reception light radiated from the endface 4 a of the optical transmission medium 4 is transmitted through thereflecting surface S2 so as to be received by the photodetector 3.

The above-described tenth embodiment of the optical communicationapparatus 10I is arranged in the casing 20, as shown in FIG. 24, showinga cross-section of the respective component parts of FIG. 23 arranged inthe casing 20.

In the present tenth embodiment of the optical communication apparatus10I, the transmission light falls on the end face 4 a of the opticaltransmission medium 4 at substantially the right angle, whereby lowdispersion is achieved. Moreover, since the photodetector 3 can bearranged below the reflecting surface S2, the apparatus can be reducedin size.

Also, in the present tenth embodiment of the optical communicationapparatus 10I, as in the first to eighth embodiments, it is possible toreduce the size and the production cost of the apparatus, while it ispossible to prevent the signal S/N ratio from being lowered.

A specified embodiment of the optical component 2 used in the respectivefirst to tenth embodiments is hereinafter explained. In the followingdescription, parts or components which are the same as those of thefirst embodiment are depicted by the same reference symbols and are notexplained specifically.

FIG. 25 shows a schematic perspective view showing the optical component2A of the first specified embodiment used in any of the first to tenthembodiments. In FIG. 25, the light source 1 is also shown.

On the lens surface S1 of the present first specified embodiment facingthe light source 1 is formed a lens portion S1 a responsible for thelens function. The lens portion S1 a is formed only on the portion ofthe lens surface S1 illuminated by a light beam La of the light sourceradiated from the light source 1. The lens portion S1 a is shaped toconform to the far-field pattern of the light beam of the light sourceLa and has different numerical aperture NA and different far-fieldpatterns of the light beam of the light source La depending on thefar-field pattern of the light beam of the light source La. The lensportion S1 a converges the incident light beam by its lens function.

FIG. 26 shows the arraying state of the substrate 11, support base 12,light source 1, optical component 2A, photodetector 3 and the opticaltransmission medium 4 in case the optical component 2A of the firstspecified embodiment is applied to the aforementioned first embodimentof the optical communication apparatus 10, whilst FIG. 27 shows aperspective view of the optical communication apparatus havingrespective components shown in FIG. 26 arranged in the casing 20. In theembodiments of FIGS. 26 and 27, the transmission light radiated from thelight source 1 is reflected by the reflection surface S2 to fall on theend face 4 a of the optical transmission medium 4, as the transmissionlight is converged by the lens portion S1 a of the optical component 2A.FIGS. 26 and 27 show an embodiment in which the optical component 2A ofthe first specified embodiment is applied to the aforementioned firstembodiment, however, the optical component 2A may also be applied to thesecond to tenth embodiments.

In the optical communication apparatus having t the optical component 2Aof the first specified embodiment, in which the lens portion S1 a shapedto conform to the far-field pattern of the light beam of the lightsource La is formed on the lens surface S1 of the optical component 2A,the light beam of the light source La, issued from the light source 1,can be caused to fall wastelessly into the optical component 2A to fallon the end face 4 a of the optical transmission medium 4.

FIG. 28 shows a schematic perspective view of the optical component 2Dof a second specified embodiment used in any of the first to tenthembodiments. Meanwhile, FIG. 28 also shows a light source 1.

The optical component 2D of the present second embodiment is constitutedby a transparent member which is in the shape of a rod having its longaxis extending along the direction of the optical axis of the lightradiated from the light source 1, that is a transparent member having asubstantially circular cross-sectional shape when the optical component2D is cut in a plane perpendicular to the optical axis of the lightradiated from the light source 1 to get to the reflective surface S2.This rod-like optical component 2D has its one end formed as e.g., aspherical lens surface S1 for producing the lens function, while havingthe opposite end as the aforementioned reflecting surface S2 having apre-set angle for allowing for total reflection of the light. Since theoptical component 2D of the present second specified embodiment isrod-shaped, the coupling surface S4, provided in the proceedingdirection of the light reflected by the reflecting surface S2, is notplanar but curved in profile.

FIG. 29 shows the arraying state of the substrate 11, support base 12,light source 1, optical component 2D, photodetector 3 and the opticaltransmission medium 4 in case the optical component 2A of the firstspecified embodiment is applied to the aforementioned first embodimentof the optical communication apparatus 10, whilst FIG. 30 shows aperspective view of the optical communication apparatus havingrespective components shown in FIG. 29 arranged in the casing 20. In theembodiments of FIGS. 29 and 30, the transmission light radiated from thelight source 1 is reflected by the reflection surface S2 to fall on theend face 4 a of the optical transmission medium 4, via coupling surfaceS4, as the transmission light is converged by the lens portion S1 a ofthe optical component 2A. FIGS. 29 and 30 show an embodiment in whichthe optical component 2D of the first specified embodiment is applied tothe aforementioned first embodiment, however, the optical component 2Amay also be applied to the second to tenth embodiments.

If the optical component 2D of the present second specified embodimentis used, the curved coupling surface S4 has the lens function, so thatthe transmission light radiated from the light source 1, converged bythe lens surface S1 and reflected by the reflecting surface S2 isfurther converged by the coupling surface S4, as a result of which itbecomes possible to reduce the focal length from the coupling surface S4to the end face 4 a of the optical transmission medium 4. If, in thesecond and fourth embodiments, the optical component 2D and thephotodetector 3 are arranged in the same area, with the reception lightradiated from the end face 4 a of the optical transmission medium 4being made to fall on the optical component 2D via the coupling surfaceS4, the reception light radiated from the incident on the couplingsurface S4 to fall on the end face 4 a of the optical transmissionmedium 4 is converged by the lens function furnished by the curvedsurface of the coupling surface S4, as a result of which the distancefrom the coupling surface S4 to the photodetector 3 can be reduced.Moreover, in the present embodiment, the reception light is incident onthe photodetector 3, as the light is converged thereon, without beingdiffused, due to the lens function furnished by the curved surface ofthe coupling surface S4. Thus, the reception light can be made to fallefficiently on the photodetector 3.

FIG. 31 shows a schematic perspective view of the optical component 2Bof the third specified embodiment used in any of the first to tenthembodiments. Meanwhile, FIG. 31 also shows the light source 1.

In the present third embodiment of the optical component 2B, the lenssurface S1 facing the light source 1, has a columnar-shaped surfacehaving a curvature only in the x-direction, or a so-called cylindricalsurface. This columnar-shaped lens surface S1 operates for convergingonly the x-direction component of the incident light beam. Thus, in thepresent third specified embodiment of the optical component 2B, if thefar-field pattern of the light beam of the light source La iselliptically-shaped with the long axis being in the x-direction, thelight beam of the light source La is made to fall wastelessly on theoptical component 2B so as to be converged thereon.

FIG. 32 shows the arraying state of the substrate 11, support base 12,light source 1, optical component 2B, photodetector 3 and the opticaltransmission medium 4 in case the optical component 2B of the thirdspecified embodiment shown in FIG. 31 is applied to the aforementionedfirst embodiment of the optical communication apparatus 10, whilst FIG.33 shows a perspective view of the optical communication apparatushaving respective components of FIG. 32 arranged in the casing 20. Inthe embodiments of FIGS. 32 and 33, the transmission light radiated fromthe light source 1 is reflected by the reflection surface S2 to fall onthe end face 4 a of the optical transmission medium 4, via couplingsurface S4, as the transmission light is converged by the lens portionS1 of the optical component 2B. FIGS. 32, 33 show an embodiment in whichthe optical component 2B of the third specified embodiment is applied tothe aforementioned first embodiment, however, the optical component 2Bmay also be applied to the second to tenth embodiments.

In the optical communication apparatus, employing the optical component2B of the third specified embodiment, the lens surface S1 of the opticalcomponent 2B is formed as a columnar-shaped cylindrical surface havingthe curvature only in the x-direction. Thus, as compared to theabove-described first specified embodiment of the optical component 2A,the optical axis adjustment tolerance in the y-direction of the opticalcomponent 2B is released to reduce the assembling cost. Also, in theoptical communication apparatus employing the third specified embodimentof the optical component 2B, in which the lens surface S1 of the opticalcomponent 2B operates for converging only the x-components of theincident light beam, if the far-field pattern of the light beam of thelight source is elliptically-shaped with the long axis lying in thex-direction, it becomes possible to cause the light beam of the lightsource La emitted by the light source 1 to be incident and convergedeffectively and wastelessly in the optical component 2B.

FIG. 34 shows a schematic perspective view of the optical component 2Cof the fourth specified embodiment used in any of the first to tenthembodiments. Meanwhile, FIG. 34 also shows the light source 1.

In the foregoing explanation of the first to tenth embodiments, theoptical component 2 is taken as an example, in which the cross-sectionalshape of the lens surface portion S1 thereof obtained on slicing theoptical component 2 in a plane perpendicular to the substrate 11 andcontaining the optical axis of light radiated from the light source 1 toget to the reflecting surface S2 is curved and convexed towards thelight source 1, as shown in FIGS. 1, 2, 5 to 15 and 17 to 20. It ishowever possible to use as the optical component used in each of thefirst to tenth embodiments such an optical component 2C in which thecross-sectional shape of the lens surface portion S1 thereof obtained onslicing the optical component 2 in a plane perpendicular to thesubstrate 11 and containing the optical axis of light radiated from thelight source 1 to get to the reflecting surface S2 is linear, and inwhich the cross-sectional shape of the lens surface portion S1 thereofobtained on slicing the optical component 2 in a plane transverse to thesubstrate 11 and containing the optical axis of light radiated from thelight source 1 to get to the reflecting surface S2 is curved andconvexed towards the light source 1, as shown in FIG. 34.

Specifically, the present fourth embodiment of the optical component 2Chas its lens surface S1 facing the light source 1 formed as acolumnar-shaped surface having a curvature only in the y-direction inthe drawing, that is a so-called cylindrical surface. Thiscolumnar-shaped lens surface S1 operates for converging only they-direction component of the incident light beam. Thus, in the presentfourth specified embodiment of the optical component 2C, if thefar-field pattern of the light beam of the light source La, radiated bythe light source 1, is elliptically-shaped, with the long axis lyingalong the y-axis, the light beam of the light source La in particular isincident and converged wastelessly and efficiently in the opticalcomponent 2C.

FIG. 35 shows an arraying state of the substrate 1, support base 12,light source 1, optical component 2C of the fourth specified embodimentshown in FIG. 34, photodetector 3 and the optical transmission medium 4in case the optical component 2C is applied to the aforementioned firstembodiment of the optical communication apparatus 10, whilst FIG. 36shows a perspective view of the optical communication apparatus havingrespective components of FIG. 35 arranged in the casing 20. In theembodiments of FIGS. 35 and 36, the transmission light radiated from thelight source 1 is reflected by the reflection surface S1, as only they-direction component of the transmission light radiated by the lightsource 1 is converged by the lens surface portion S1 which is thecylindrical surface of the optical component 2C. FIGS. 35, 36 show anembodiment in which the optical component 2C of the fourth specifiedembodiment is applied to the aforementioned first embodiment, however,the optical component 2C may also be applied to the second to tenthembodiments.

In the optical communication apparatus, employing the optical component2C of the fourth specified embodiment, the lens surface S1 of theoptical component 2C is formed as a columnar-shaped cylindrical surfacehaving the curvature only in the y-direction. Thus, as compared to theabove-described first specified embodiment of the optical component 2A,the optical axis adjustment tolerance in the x-direction of the opticalcomponent 2C is released to reduce the assembling cost. Also, in theoptical communication apparatus employing the fourth specifiedembodiment of the optical component 2C, in which the lens surface S1 ofthe optical component 2C operates for converging only the y-componentsof the incident light beam, if the far-field pattern of the light beamof the light source La is elliptically-shaped with the long axis lyingin the x-direction, it becomes possible to cause the light beam of thelight source La emitted by the light source 1 to be incident andconverged effectively and wastelessly in the optical component 2B.

The foregoing description is directed to the optical communicationapparatus of respective embodiments and optical components of therespective specified embodiments. However, the present invention may beoptionally changed without being limited to the above-describedembodiments and specified embodiments. For example, in theabove-described embodiments and specified embodiments, the totalreflection of light is produced for reflecting the light on thereflecting surface S2 of the optical component 2 or the opticalcomponents 2A to 2D. However, the reflecting surface S2 may be processedwith mirror surface finishing to produce reflection to guide thetransmission light towards the optical transmission medium 4. Thepresent invention also is not limited to optical communication and maybe applied to a number of usages employing light transmission/reception.

INDUSTRIAL APPLICABILITY

In the optical communication apparatus according to the presentinvention, in which the transmission light from a light source isconverged on a first surface of a sole optical component and reflectedtowards an optical transmission medium and in which the light incidenton the light reception element without falling on the second surface ofthe optical component is detected as the reception light, it is possibleto reduce the cost and size of the apparatus without lowering thetransmission/reception performance.

Also, in the optical apparatus of the present invention, thetransmission light from the light source is reflected by the totalreflection on the second surface of the optical component, so that, ascompared to the conventional apparatus employing e.g., a polarizationbeam splitter, it is unnecessary to form a high reflection multi-layerfilm or a polarization beam splitter film, whilst the film-forming costor the cost of bonding two prisms together to form a polarization beamsplitter can be dispensed with.

Moreover, with the optical apparatus of the present invention, in whichthe optical component is arranged above the light receiving element, theapparatus can be further reduced in size.

With the optical apparatus of the present invention, in which the secondsurface of the optical component is inclined at an angle of 45° relativeto the plane in which the optical component is arranged, the opticalcomponent can be fabricated easily to enable further cost reduction.

With the optical apparatus of the present invention, a diffractivepattern producing the light converging operation is formed on the firstsurface of the optical component, it becomes possible to increase therefractive power further to enable further reduction in size of theapparatus. Moreover, since the aberration can be corrected easily, it ispossible to improve the S/N ratio.

With the optical apparatus of the present invention, the opticalcomponent is provided with a surface operating to prevent the componentfrom becoming acute in shape to prevent kicking of the reception lightto improve operational safety and to render the optical component lesssusceptible to destruction.

Also, with the optical apparatus of the present invention, the firstsurface of the optical component is shaped to conform to the lightspreading pattern of the light radiated from the light source, so thatthe light radiated from the light source is caused to be incident andconverged wastelessly and effectively in the optical component.

What is claimed is:
 1. An optical apparatus, comprising: a main bodyunit; a connector; an optical transmission medium connected to the mainbody unit by the connector, the optical transmission medium comprisingan end face; a light emitting element configured to radiate atransmission signal; a light receiving element comprising a surfacepositioned to receive a reception signal from the optical transmissionmedium so as to define a reception optical path; and an opticalcomponent comprising a body enclosed by at least a second surfacedisposed at an acute angle relative to the surface of the lightreceiving element and configured to substantially reflect bothS-polarized light and P-polarized light incident on the second surface,a first surface disposed between the second surface and the lightemitting source, a supporting surface disposed between the first surfaceand the second surface, and a coupling surface disposed between thefirst surface and the second surface and between the supporting surfaceand the end face of the optical transmission medium.
 2. The opticalapparatus of claim 1, wherein at least one of a structural andpositional relationship between at least two of the optical mediumtransmission, the optical component, and the light receiving element issuch that the reception optical path does not intersect the secondsurface of the optical component.
 3. The optical apparatus of claim 2,wherein the light emitting element is disposed on a first side of thesecond surface and at least part of the optical transmission medium isdisposed on a second side of the second surface.
 4. The opticalapparatus of claim 3, wherein the optical transmission medium isarranged so that the reception optical path is at an angle to thesurface of the light receiving element.
 5. The optical apparatus ofclaim 3, wherein the optical component further comprises a cut outsurface disposed between the coupling surface and the second surfacesuch that the entire optical transmission medium is disposed on thesecond side of the second surface.
 6. The optical apparatus of claim 2,wherein the light emitting element is disposed on a first side of thesecond surface and the optical transmission medium is disposed on thefirst side of the second surface.
 7. The optical apparatus of claim 6,wherein the light receiving element is disposed on a second side of thesecond surface.
 8. The optical apparatus of claim 6, wherein the opticaltransmission medium is arranged so that the reception optical path is atan angle to the surface of the light receiving element.
 9. The opticalapparatus of claim 6, wherein the light receiving element is disposedbetween the first surface and the light emitting element.
 10. Theoptical apparatus of claim 1, wherein the first surface comprises adiffraction grating pattern.
 11. The optical apparatus of claim 1,wherein a positional relationship between the optical mediumtransmission, the optical component, and the light receiving element issuch that the reception optical path intersects the second surface ofthe optical component.
 12. The optical apparatus of claim 1, wherein thelight emitting element is configured to radiate the transmission signalalong an optical path that is at an acute angle to the surface of thelight receiving element.
 13. The optical apparatus of claim 1, whereinthe first surface comprises a convex shape that extends towards thelight emitting element.
 14. The optical apparatus of claim 13, whereinthe convex shape of the first surface is curved in a plane passingthrough the light emitting element and the optical transmission medium.15. The optical apparatus of claim 13, wherein the convex shape of thefirst surface is flat in a plane passing through the light emittingelement and the optical transmission medium.
 16. The optical apparatusof claim 13, wherein the convex shape of the first surface is curved ina first plane passing through the light emitting element and the opticaltransmission medium and curved in a second plane that passesperpendicularly through the first plane.
 17. The optical apparatus ofclaim 16, wherein the first surface of the optical component furthercomprises a surface extending from the convex shape and wherein thefirst surface is configured to substantially transmit at least one ofS-polarized light and P-polarized light incident on the first surface.